Solid electrolytic capacitor and method for producing the same

ABSTRACT

Disclosed are a solid electrolytic capacitor comprising a valve-acting metal, an oxide dielectric layer formed on a surface of the valve-acting metal and a solid electrolyte layer provided on the dielectric film layer, in which the electrically conducting polymer composition layer contains as a dopant at least one anion selected from (1) an alkoxy-substituted naphthalene monosulfonate anion, (2) a heterocyclic sulfonate anion, and (3) an anion of an aliphatic polycyclic compound or a combination thereof with another anion having a dopant ability and a method for producing such a solid electrolytic capacitor.The solid electrolytic capacitor of the invention is excellent in voltage resistance, high frequency property, tan delta, leakage current, heat resistance (reflow property), etc.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is an application pursuant to Article 111,Section (a) of 35 U.S.C. with claiming in compliance with Article 119,Section (e)(i) the benefit of earlier application dates of ProvisionalApplications Nos. 60/123,985 and 60/123,986, filed on Mar. 11, 1999 forthe both, filed under Article 111, Section (b).

TECHNICAL FIELD

The present invention relates to a solid electrolytic capacitor and to aproduction method thereof. More specifically, the present inventionrelates to a solid electrolytic capacitor comprising a solid electrolytehaving thereon an electrically conducting polymer having a πelectron-conjugated system containing as a dopant at least one organicanion selected from (1) an alkoxy-substituted naphthalene monosulfonateanion, (2) a sulfonate anion of a heterocyclic compound, and (3) ananion of an aliphatic polycyclic compound and also relates to aproduction method of the capacitor. Preferably, the present inventionrelates to a solid electrolytic capacitor comprising a solid electrolyteadditionally containing another anion having a dopant ability other thanthe organic anion dopant, and also relates to a production method of thecapacitor.

BACKGROUND ART

A solid electrolytic capacitor is a device where an oxide film layer, adielectric material, is formed on an anode substrate comprising a metalfoil subjected to etching treatment, a solid semiconductor layer(hereinafter, simply referred to as a solid electrolyte) is formed as anopposing electrode outside the oxide dielectric layer and preferably anelectric conductor layer such as an electrically conducting paste isfurther formed thereon. The device is actually used after the entiredevice is completely sealed by an epoxy resin or the like.

For the solid electrolyte, it has been heretofore known to use, forexample, an inorganic semiconductor material such as manganese dioxideand lead dioxide, a tetracyanoquinodimethane (TCNQ) complex salt, anintrinsic electrically conducting polymer having an electricconductivity in the range of from 10⁻³ to 5×10³ S/cm(JP-A-1-169914 (theterm “JP-A” as used herein means an “unexamined published Japanesepatent application”(U.S. Pat. No. 4,803,596)) or a π-conjugated polymersuch as polyaniline (JP-A-61-239617), polypyrrole (JP-A-61-240625),polythiophene derivative (JP-A-2-15611 (U.S. Pat. No. 4,910,645)) orpolyisothianaphthene (JP-A-62-118511). Many of these electricallyconducting polymers, which comprise a polymer main chain having aπ-conjugated repeating structural unit and a dopant contained in thepolymer chain, are used as an electrically conducting polymer layer (ora polymer-type charge-transfer complex). Furthermore, in recent years,not only dopants are used singly but also they are used in combinationwith, for example, manganese dioxide (JP-B-6-101418 (the term “JP-B” asused herein means an “examined Japanese patent publication” (U.S. Pat.No. 4,959,753)) or a filler (JP-A-9-320901).

With respect to the method for forming a solid electrolyte layer, amethod of fusing and thereby forming an electrically conducting polymerlayer on a dielectric layer provided on a valve-acting metal surfacehaving a microfine void structure and a method of producing theabove-mentioned electrically conducting polymer on a dielectric layerhave been conventionally known. More specifically, for example, in thecase of using a polymer of a 5-membered heterocyclic compound such aspyrrole or thiophene, a method of dipping an anode foil in a loweralcohol/water-based solution of a 5-membered heterocyclic compound andthen dipping the anode foil in an aqueous solution having dissolvedtherein an oxidizing agent and an electrolyte to give rise to chemicalpolymerization, thereby forming an electrically conducting polymer(JP-A-5-175082), and a method of applying a 3,4-dioxyethylenethiophenemonomer and an oxidizing agent each preferably in the form of a solutionto an oxide coating layer of a metal foil separately differing in timeor simultaneously to thereby form a solid electrolyte layer(JP-A-2-15611 (U.S. Pat. No. 4,910,645)) and JP-A-10-32145(EP-A-820076(A2), (the term “EP-A” as used herein means an “unexaminedpublished European patent application”)) are known.

In particular, JP-A-10-32145 discloses polymers of a monomer selectedfrom pyrrole, thiophene, furan, aniline and derivatives thereof anddoped with an aromatic polysulfonic acid (e.g., naphthalene disulfonicacid) having a plurality of sulfonic acid groups in the molecularstructure thereof, and also discloses a polymerization method as theproduction method of the polymer, where a mixed solution of theabove-described polymerizable monomer and an oxidizing agent is coatedand dried or an oxidizing agent is introduced and then the polymerizablemonomer is introduced.

Also, JP-A-10-32145 discloses a production method using the dopant ofthe above-described aromatic polysulfonic acid as a constituentcomponent of the oxidizing agent (ferric salt), stating that the solidelectrolytic capacitor comprising this dopant has excellent effects onthe high temperature resistance or to prevent deterioration in thestatic capacitance.

Furthermore, JP-B-6-82590 (U.S. Pat. No. 4,959,753) discloses a solidelectrolytic capacitor containing as a dopant an alkylnaphthalenesulfonate anion substituted by one or more alkyl groups, which hasexcellent effects on the initial property or leakage current property.

Known examples of the oxidizing agent for use, for example, in thechemical polymerization of 5-membered heterocyclic compounds such asthiophene include iron(III) chloride, Fe(ClO₄)₃, organic acid iron(III)salt, inorganic acid iron(III) salt, alkyl persulfate, ammoniumpersulfate (hereinafter simply referred to as “APS”), hydrogen peroxide,K₂Cr₂O₇ (see, JP-A-2-15611 (U.S. Pat. No. 4,910,645)), cupric compoundsand silver compounds (see, JP-A-10-32145 (EP-A-820076(A2))).

However, the capacitor comprising a solid electrolyte using themanganese dioxide is disadvantageous in that the oxide dielectric filmlayer is ruptured at the thermal decomposition of manganese nitrate andthe impedance property is not satisfied. In the case of using leaddioxide, its effect on the environment must be taken into account. Thecapacitor comprising a solid electrolyte using a TCNQ complex salt hasgood heat fusion workability and excellent electric conductivity but theTCNQ complex salt itself has a problem in the heat resistance andaccordingly, the soldering heat resistance is poorly reliable. In orderto overcome these problems, an electrically conducting polymer such aspolypyrrole is applied to the solid electrolyte on the surface of adielectric by electrolytic polymerization or chemical polymerization butsatisfactory results cannot be obtained with respect to the homogeneityof film, soldering heat resistance, impedance property and the like.

Demands for the production of a capacitor device having high performanceare recently increasing and to cope with this tendency, furtherimprovements are required on the material for the solid electrolyte,production method thereof, heat stability, homogeneity of the film andthe like.

DISCLOSURE OF THE INVENTION

Under these circumstances, an object of the present invention is toprovide a solid electrolytic capacitor having excellent propertiessatisfying the requirements with respect to the reduction in the weightand size, high capacity, high frequency property, tan δ, leakagecurrent, heat resistance (reflow property), durability, etc. Inparticular, an object of the present invention is to provide a heatresistant solid electrolytic capacitor having excellent low impedanceproperty and exhibiting durability in a sparking voltage test.

In order to attain the above-described objects, the present inventorshave made extensive investigations on the kind, combination and contentof a dopant anion in the electrically conducting polymer which works outto a solid electrolyte and as a result, they have now found that theabove-described object of the present invention can be accomplished byprovision of a specified organic anion in the solid electrolyteconcerned in a solid electrolytic capacitor comprising opposingelectrodes, one part electrode being a dielectric layer comprising ametal oxide and having a microfine structure provided on the surface ofa valve-acting metal foil, and a solid electrolyte comprising anelectrically conducting polymer formed on the dielectric layer.

More specifically, the present invention provides a solid electrolyticcapacitor, which is compact and has high-performance, low impedance andexhibiting durability in a sparking voltage test, wherein the solidelectrolyte contains as a dopant at least one organic anion selectedfrom (1) an alkoxy-substituted naphthalene monosulfonate anionsubstituted by at least one linear or branched, saturated or unsaturatedalkoxy group having 1 to 12 carbon atoms, (2) a sulfonate anion of aheterocyclic compound having a 5- or 6-membered heterocyclic ring(hereafter, referred to as heterocyclic sulfonate anion), and (3) ananion of an aliphatic polycyclic compound. The present invention alsoprovides a production method of such a solid electrolytic capacitor.

The present invention provides the following:

[1] A solid electrolytic capacitor comprising an oxide dielectric filmhaving provided thereon an electrically conducting polymer layercontaining a π electron-conjugated structure, wherein the polymer layercontains as a dopant at least one organic anion selected from (1) analkoxy-substituted naphthalene monosulfonate anion substituted by atleast one linear or branched, saturated or unsaturated alkoxy grouphaving from 1 to 12 carbon atoms, (2) a sulfonate anion of aheterocyclic compound having a 5- or 6-membered heterocyclic ring(hereinafter referred to as a “heterocyclic sulfonate anion”), and (3)an anion of an aliphatic polycyclic compound.

[2] The solid electrolytic capacitor as described in 1 above, whereinthe organic anion as a dopant is an alkoxy-substituted naphthalenemonosulfonate anion substituted by at least one linear or branched,saturated or unsaturated alkoxy group having from 1 to 12 carbon atoms.

[3] The solid electrolytic capacitor as described in 2 above, wherein atleast one hydrogen on an aromatic ring of the alkoxy-substitutednaphthalene monosulfonate is substituted by a substituent selected froma halogen atom, a nitro group, a cyano group, and a trihalomethyl group.

[4] The solid electrolytic capacitor as described in 1 above, whereinthe organic anion as a dopant is an anion of heterocyclic sulfonateanion.

[5] The solid electrolytic capacitor as described in 4 above, whereinthe heterocyclic sulfonate anion is an anion having heterocyclicskeleton selected from the group consisting of compounds containing achemical structure of morpholine, piperidine, piperazine, imidazole,furan, 1,4-dioxane, benzimidazole, benzothiazolylthio, benzisoxazole,benzotriazole or benzofuran.

[6] The solid electrolytic capacitor as described in 4 above, whereinthe heterocyclic sulfonate anion contains at least one alkylsulfonatesubstituent in the chemical structure thereof.

[7] The solid electrolytic capacitor as described in 1 above, whereinthe organic anion as a dopant is an anion of an aliphatic polycycliccompound.

[8] The solid electrolytic capacitor as described in 1 above, whereinthe organic anion is contained in an amount of from about 0.1 to about50 mol % based on all the repeating structural units of the electricallyconducting polymer.

[9] The solid electrolytic capacitor as described in 1 above, wherein inaddition to the organic anion, a reductant anion of an oxidizing agenthaving a dopant ability is contained in an amount of from about 0.1 toabout 10 mol %.

[10] The solid electrolytic capacitor as described in 9 above, whereinthe reductant anion of an oxidizing agent is a sulfate ion.

[11] The solid electrolytic capacitor comprising an oxide dielectricfilm having provided thereon an electrically conducting polymer asdescribed in 1 above, wherein the electrically conducting polymercontains a repeating structural unit represented by the followinggeneral formula (I):

(wherein the substituents R¹ and R² each independently represents anyone monovalent group selected from hydrogen, a linear or branched,saturated or unsaturated alkyl group having from 1 to 6 carbon atoms, alinear or branched, saturated or unsaturated alkoxy group having from 1to 6 carbon atoms, a hydroxyl group, a halogen atom, a nitro group, acyano group, a trihalomethyl group, a phenyl group and a substitutedphenyl group, R¹ and R² may be combined to each other at any position toform at least one divalent chain for forming at least one 5-, 6- or7-membered saturated or unsaturated ring structure, X represents ahetero atom selected from S, O, Se, Te or NR³, R³ represents hydrogen, alinear or branched, saturated or unsaturated alkyl group having from 1to 6 carbon atoms, a phenyl group or a linear or branched, saturated orunsaturated alkoxy group having from 1 to 6 carbon atoms, the alkylgroup and the alkoxy group represented by R¹, R² or R³ may optionallycontain in the chain thereof a carbonyl bond, an ether bond, an esterbond, an amide bond or an imino bond, and δ is from 0 to 1).

[12] The solid electrolytic capacitor as described in 11 above, whereinthe repeating structural unit represented by formula (I) is a chemicalstructure represented by the following general formula (II):

(wherein the substituents R⁴and R⁵ each independently representshydrogen, a linear or branched, saturated or unsaturated alkyl grouphaving from 1 to 6 carbon atoms or a substituent for forming at leastone 5-, 6- or 7-membered heterocyclic structure containing the twooxygen elements shown in the formula by combining the linear orbranched, saturated or unsaturated alkyl groups having from 1 to 6carbon atoms to each other at any position, the ring structure formed inthe scope thereof includes a chemical structure such as a substitutedvinylene group and a substituted o-phenylene group, and δ is from 0 to1).

[13] A method for producing a solid electrolytic capacitor comprising anoxide dielectric film having provided thereon an electrically conductingpolymer composition layer described in 1 above, the method comprisingpolymerizing a polymerizable monomer compound on an oxide dielectricfilm by an oxidizing agent, wherein the polymerizable monomer compoundis a compound represented by the following general formula (III):

(wherein R¹, R² and X are the same as defined in the general formula (I)above) and the polymerization reaction takes place in the presence of acompound capable of providing at least one organic anion selected from(1) an alkoxy-substituted naphthalene monosulfonate anion substituted byat least one linear or branched, saturated or unsaturated alkoxy grouphaving from 1 to 12 carbon atoms, (2) a sulfonate anion of aheterocyclic compound having a 5- or 6-membered heterocyclic ring(hereinafter referred to as a “heterocyclic sulfonate anion”), and (3)an anion of an aliphatic polycyclic compound.

[14] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein the polymerizable monomer compoundrepresented by formula (III) is a compound represented by wing generalformula (IV):

(wherein R⁴ and R⁵ are the same as defined in the general formula

[15] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of dipping avalve-acting metal anode foil having formed thereon an oxide dielectricfilm layer in a solution containing a polymerizable monomer compound anda step of dipping the metal anode foil in a solution containing anoxidizing agent and above-described organic anion.

[16] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of dipping avalve-acting metal anode foil having formed thereon an oxide dielectricfilm layer in a solution containing an oxidizing agent and a step ofdipping the metal anode foil in a solution containing a polymerizablemonomer compound and above-described organic anion.

[17] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of dipping avalve-acting metal anode foil having formed thereon an oxide dielectricfilm layer in a solution containing an oxidizing agent and then a stepof dipping the metal anode foil in a solution containing a polymerizablemonomer compound and above-described organic anion.

[18] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of dipping avalve-acting metal anode foil having formed thereon an oxide dielectricfilm layer in a solution containing a polymerizable monomer compound andthen a step of dipping the metal anode foil in a solution containing anoxidizing agent and above-described organic anion.

[19] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of dipping avalve-acting metal anode foil having formed thereon an oxide dielectricfilm layer in a solution containing an oxidizing agent andabove-described organic anion and then a step of dipping the metal anodefoil in a solution containing a polymerizable monomer compound.

[20] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of dipping avalve-acting metal anode foil having formed thereon an oxide dielectricfilm layer in a solution containing a polymerizable monomer compound andabove-described organic anion and then a step of dipping the metal anodefoil in a solution containing an oxidizing agent.

[21] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of repeatingmultiple times a process of dipping a valve-acting metal anode foilhaving formed thereon an oxide dielectric film layer in a solutioncontaining an oxidizing agent and above-described organic anion and thena process of dipping the metal anode foil in a solution containing apolymerizable monomer compound.

[22] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of repeatingmultiple times a process of dipping a valve-acting metal anode foilhaving formed thereon an oxide dielectric film layer in a solutioncontaining a polymerizable monomer compound and above-described organicanion and then a process of dipping the metal anode foil in a solutioncontaining an oxidizing agent.

[23] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of repeatingmultiple times a process of dipping a valve-acting metal anode foilhaving formed thereon an oxide dielectric film layer in a solutioncontaining an oxidizing agent and then a process of dipping the metalanode foil in a solution containing a polymerizable monomer compound andabove-described organic anion.

[24] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of repeatingmultiple times a process of dipping a valve-acting metal anode foilhaving formed thereon an oxide dielectric film layer in a solutioncontaining a polymerizable monomer compound and then a process ofdipping the metal anode foil in a solution containing an oxidizing agentand above-described organic anion.

[25] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of repeatingmultiple times a process of dipping a valve-acting metal anode foilhaving formed thereon an oxide dielectric film layer in a solutioncontaining an oxidizing agent and above-described organic anion and thena process of dipping the metal anode foil in a solution containing apolymerizable monomer compound, followed by a step of washing and dryingthe metal anode foil.

[26] The method for producing a solid electrolytic capacitor as claimedin claim 13, wherein said method comprises a step of repeating multipletimes a process of dipping a valve-acting metal anode foil having formedthereon an oxide dielectric film layer in a solution containing apolymerizable monomer compound and above-described organic anion andthen a process of dipping the metal anode foil in a solution containingan oxidizing agent, followed by a step of washing and drying the metalanode foil.

[27] The method for producing a solid electrolytic capacitor as claimedin claim 13, wherein said method comprises a step of repeating multipletimes a process of dipping a valve-acting metal anode foil having formedthereon an oxide dielectric film layer in a solution containing anoxidizing agent and then a process of dipping the metal anode foil in asolution containing a polymerizable monomer compound and above-describedorganic anion, followed by a step of washing and drying the metal anodefoil.

[28] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein said method comprises a step of repeatingmultiple times a process of dipping a valve-acting metal anode foilhaving formed thereon an oxide dielectric film layer in a solutioncontaining a polymerizable monomer compound and then a process ofdipping the metal anode foil in a solution containing an oxidizing agentand above-described organic anion, followed by a step of washing anddrying the metal anode foil.

[29] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein the organic anion is analkoxy-substituted naphthalene monosulfonate anion substituted by atleast one linear or branched, saturated or unsaturated alkoxy grouphaving from 1 to 12 carbon atoms.

[30] The method for producing a solid electrolytic capacitor asdescribed in 29 above, wherein at least one hydrogen on an aromatic ringof the alkoxy-substituted naphthalene monosulfonate anion is substitutedby a substituent selected from a halogen atom, a nitro group, a cyanogroup, and a trihalomethyl group.

[31] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein the organic anion is a heterocyclicsulfonate anion.

[32] The method for producing a solid electrolytic capacitor asdescribed in 31 above, wherein the heterocyclic sulfonate anion is ananion having at least one heterocyclic skeleton selected from the groupconsisting of compounds containing a chemical structure of morpholine,piperidine, piperazine, imidazole, furan, 1,4-dioxane, benzimidazole,benzothiazolylthio, benzisoxazole, benzotriazole or benzofuran.

[33] The method for producing a solid electrolytic capacitor asdescribed in 31 above, wherein the heterocyclic sulfonate anion containsat least one alkylsulfonate substituent in the chemical structurethereof.

[34] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein the organic anion as a dopant is an anionof an aliphatic polycyclic compound.

[35] The method for producing a solid electrolytic capacitor asdescribed in 13 above, wherein the oxidizing agent is a persulfate.

[36] The solid electrolytic capacitor as described in 1 above, whereinthe solid electrolyte has at a portion which is of a lamellar structure.

[37] The solid electrolytic capacitor as described in 13 above, whereinthe solid electrolyte having at a portion which is of a lamellarstructure is formed on an outer surface of the dielectric film or on anouter surface and inside a fine pore portion thereof.

[38] The solid electrolytic capacitor as described in 36 above, whereinadjacent lamellae define an interstitial space therebetween over atleast a portion of opposing surfaces thereof.

[39] The solid electrolytic capacitor as described in 36 above, whereineach lamella of the solid electrolyte constituting the lamellarstructure is in the range of from about 0.01 to about 5 μm, and thesolid electrolyte layer has a total thickness in the range from about 1to about 200 μm.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a vertical cross-sectional view showing a representativeexample of the solid electrolytic capacitor according to the presentinvention having a valve-acting metal foil.

FIG. 2 is a scanning electron micrograph at a magnification of ×5,000 ofthe cross sectional surface of aluminum foil having a fine structurehaving formed therein an electrically conducting polymer layer inExample 32.

DETAIL DESCRIPTION OF THE INVENTION

The present invention is described in detail below.

In the present invention, the electrically conducting polymer layercontains at least one organic anion selected from (1) analkoxy-substituted naphthalene monosulfonate anion substituted by atleast one linear or branched, saturated or unsaturated alkoxy grouphaving 1 to 12 carbon atoms, (2) a sulfonate anion of a heterocycliccompound having a 5- or 6-membered hetero ring (hereafter, referred toas heterocyclic sulfonate anion), and (3) an anion of an aliphaticpolycyclic compound as a main anion having a dopant ability, so that apreferred electrically conducting polymer layer (charge-transfercomplex) having good heat resistance can be formed. As a result, ahigh-performance solid electrolytic capacitor having low impedanceproperty and excellent durability in a sparking voltage test or the likeand a production method thereof can be provided.

Furthermore, in the present invention, another anion other thanabove-described organic anion dopant is used as a dopant in combination,therefore, higher performance in the above-described properties can beattained.

The π electron-conjugated polymer in an electrically conducting polymerlayer suitable for the capacitor of the present invention is a polymerhaving a π electron-conjugated system in the polymer main chainstructure. Specific examples thereof include polyaniline,poly-p-phenylene, poly-p-phenylenevinylene, polythienylenevinylene,polyheterocyclic polymer and substituted derivatives thereof. Preferredexamples of the polyheterocyclic polymers include a πelectron-conjugated polymer comprising a structural unit represented bygeneral formula (I), and more preferrably a π electron-conjugatedpolymer comprising a structural unit represented by general formula(II).

In general formulae (I) and (III) above, useful examples of the linearor branched, saturated or unsaturated alkyl group having 1 to 6 carbonatoms represented by the substituents R¹, R² or R³, include methyl,ethyl, vinyl, propyl, allyl, isopropyl, butyl and 1-butenyl. Usefulexamples of the linear or branched, saturated or unsaturated alkoxygroup having from 1 to 6 carbon atoms include methoxy, ethoxy, propoxy,isopropoxy and butoxy. Useful examples of the substituent other than theabove-described alkyl group and alkoxy group include a nitro group, acyano group, a phenyl group and a substituted phenyl group (e.g., phenylgroups substituted by a halogen group such as Cl, Br, F, etc.). Thealkyl group or alkoxy group in R¹ or R² may optionally contain in thechain thereof a carbonyl bond, an ether bond, an ester bond, an amidebond or an imino bond, and particularly useful examples thereof includea methoxyethoxy group and a methoxyethoxyethoxy group.

The substituents R¹ and R² may be combined to each other at any positionto form at least one divalent chain for forming at least one 5-, 6- or7-membered saturated or unsaturated ring structure. Specific examples ofthe structure represented by general formulae (I) or (III) include a3,4-propylene-substituted structure (V), a 3,4-butylene-substitutedstructure (VI), 3,4-butenylene-substituted structure (VII),3,4-butadienylene-substituted structure (VIII) and anaphtho[2,3-c]-condensed structure (IX).

In the above-described formulae, X represents a hetero atom and examplesthereof include S, O, Se, Te and NR³. The above-described3,4-butadienylene-substituted structure where X is S is denoted anisothianaphthenylene structure in the case of the monomer compoundstructure of general formula (I) or denoted isothianaphthene in the caseof the monomer compound structure of general formula (III). Similarly,the naptho[2,3-c]-condensed structure is denoted anaphtho[2,3-c]thienylene structure in the case of general formula (I) ordenoted naphtho[2,3-c]thiophene in the case of the monomer compoundstructure of general formula (III). In the formulae, δ represents anumber of charges per the repeating structural unit and is from 0 to 1.

Useful examples of the substituents R⁴ and R⁵ in general formulae (II)and (IV) include methyl, ethyl, propyl, isopropyl, vinyl and allyl.Furthermore, R⁴ and R⁵ may be substituents of which alkyl groups havingfrom 1 to 6 carbon atoms are bonded to each other at any position toform at least one 5-, 6- or 7-membered heterocyclic ring structurecontaining the two oxygen elements in general formulae (II) or (IV).Preferred examples thereof include 1,2-ethylene, 1,2-propylene and1,2-dimethylethylene. Furthermore, the alkyl groups each having from 1to 6 carbon atoms represented by R⁴ and R⁵ may be combined to each otherat any position to form an unsaturated hydrocarbon ring structure suchas a substituted vinylene group and a substituted o-phenylene group, andexamples thereof include 1,2-vinylene (X), 1,2-propenylene (XI),2,3-butylen-2-ene (XII), 1,2-cyclohexylene (XIII), methyl-o-phenylene(XIV), 1,2-dimethyl-o-phenylene (XV) and ethyl-o-phenylene (XVI).

Among the polymerizable monomer compounds represented by general formula(III) for use in the solid electrolytic capacitor and the productionmethod thereof of the present invention, for example, thiophene(R¹=R²=H, X=S) and pyrrole (R¹=R²=H, X=NH), or among thiophenesrepresented by general formula (IV), a polymerizable monomer compound of3,4-dioxyethylene-thiophene are known. Also, many oxidizing agents whichcan polymerize such a polymerizable monomer compound are known. However,a capacitor comprising a solid electrolyte produced from an electricallyconducting composition containing the above-described organic anion inany of (1) to (3) as a dopant or using another anion in combination asan auxiliary dopant, has been heretofore unknown.

More specifically, JP-A-10-32145 supra discloses as an electricallyconducting polymer of a capacitor only a polymer selected from pyrrole,thiophene, furan, aniline and derivatives thereof each doped with anaromatic polysulfonate compound dopant having a plurality of sulfonicacid groups in the molecular structure thereof (e.g., naphthalenedisulfonate anion). This patent publication does not disclose theorganic anion in any one of(1) to (3) above for use in the capacitor ofthe present invention. Furthermore, the excellent effect owing to theanother dopant other than the organic anion in any one of (1) to (3)above, contained in combination is unknown either.

In the solid electrolytic capacitor of the present invention, the dopantconstituting the solid electrolyte is preferably doped such that theorganic anion in any one of (1) to (3) above is contained in an amountof from about 0.1 to about 50 mol %, and more preferably another dopantother than the organic anion in any one of (1) to (3) above isadditionally contained in an amount of from about 0.1 to about 10 mol %,based on the total weight of the π-conjugated polymer composition. Byvirtue of this construction, a high-performance capacitor not onlycapable of solving the above-described problems but also favored withlow impedance property and excellent heat resistance and durability in asparking voltage test is provided. Such a capacitor has been heretoforeunknown.

The capacitor of the present invention comprises a solid electrolytecapable of providing a capacitor particularly favored with low impedanceproperty and excellent sparking voltage proof property, wherein theamount of the organic anion in any one of (1) to (3) above contained ispreferably from about 1 to about 30 mol % based on the total weight ofthe π-conjugated polymer composition.

On the other hand, the amount of another dopant contained in addition tothe above-described organic anion is preferably from about 0.1 to about5 mol % based on the total weight of the π-conjugated polymercomposition. In the production method of the present invention, where anoxidizing agent is used at the time of the polymerization of thepolymerizable monomer compound, the another dopant is contained as areduced form anion of the oxidizing agent. However, it may be separatelyadded by a different method and the method therefor is not limited.

Usually, the method for producing the above-described solid electrolyteplays an important role in the production of a capacitor for attaininghigh capacity and high frequency property and in the improvement of tanδ, leakage current, heat resistance (reflow property), impedance,durability, etc. To these effects, the combination of πelectron-conjugated structure and dopant constituting the solidelectrolyte and also the increase or improvement in the homogeneity ofthe electric conducting path by densely filling and forming anelectrically conducting polymer layer on a fine dielectric layer areimportant. In particular, the constitution of the electricallyconducting polymer has a great effect on the capacitor properties.

In the solid electrolytic capacitor according to a preferred embodimentof the present invention, at least a portion of the solid electrolytelayer is of a lamellar structure so as to have thermal stress relaxationproperties.

The solid electrolyte layer is formed in an inside of fine pore portionor on an outer surface of the dielectric material layer on the surfaceof the valve-acting metal. The thickness of the outer surface layer isin the range of from about 1 to about 200 μm, preferably from about 1 toabout 100 μm. In the present invention, the lamellar structure is formedmostly on the outer surface but it is desirable that it is also formedinside the cavity of fine pores. Most lamellae are formed substantiallyin parallel to the surface of the valve-acting metal. Adjacent lamellaedefine an interstitial space therebetween over at least a portion oftheir opposing surfaces. The thickness of each lamella or unit layerconstituting the lamellar structure is in the range of from about 0.01to about 5 μm, preferably in the range of from about 0.01 to about 1 μm,more preferably from about 0.1 to about 0.3 μm.

The production method of the solid electrolyte according to the presentinvention is characterized in that the above-described organic anion ora combination of it with another anion is contained as the dopant forthe polymer of the polymerizable monomer compound. More specifically,the present invention relates to a production method comprising a stepof causing oxidative polymerization of a polymerizable monomer compoundrepresented by general formulae (III) or (IV) on a finely porousdielectric layer in the presence of a compound capable of providing theabove-described organic anion by the action of an oxidizing agent, thepolymer produced working out to a solid electrolyte on the dielectricsurface. By performing this production step at least once, preferablyrepeating it from 3 to 30 times, per one anode substrate, a dense solidelectrolyte layer can be easily formed.

For example, in one preferred embodiment of the production process, thepolymerization step may include a step of dipping a valve-acting metalanode foil having formed thereon an oxide dielectric film layer in asolution containing an oxidizing agent (Solution 1) and a step ofdipping the anode foil in a solution containing a polymerizable monomercompound and the above-described organic anion (Solution 2), or mayinclude a step of dipping the anode foil in Solution 2 and then dippingit in Solution 1 or a step of dipping the anode foil in Solution 1 andthen dipping it in Solution 2.

In another embodiment, the production method may include a step ofdipping the anode foil in a solution containing an oxidizing agent andthe above-described anion (Solution 3) and a step of dipping the anodefoil in a solution containing a polymerizable monomer compound (Solution4) or may include a step of dipping the anode foil in Solution 4 andthen dipping it in Solution 3 or a step of dipping the anode foil inSolution 3 and then dipping it in Solution 4. Solutions 1 to 4 each maybe used in the state of a suspension.

Furthermore, the dipping step may be easily changed to a coatingoperation. Solutions 1 to 4 may be the same or different solventsystems, as needed. According to the kind of the solvent, a drying stepmay be additionally provided between the process with Solution 1 and theprocess with Solution 2 or between the process with Solution 3 and theprocess with Solution 4. After producing the solid electrolyte, a stepof washing the device with an organic solvent or with water may beprovided. In this case, it is simple and preferred to use the solventused in any of Solutions 1 to 4 as the organic solvent for use in thewashing. However, any solvent may be used as far as it can merelydissolve the polymerizable monomer compound, the above-described organicanion or the compound providing another anion having a dopant ability.By the washing with the solvent, the amount of the dopant other than theabove-described organic anion, contained in the polymer may be reduced.However, the presence of at least the above-described organic anionsometimes contributes to the properties of the solid electrolyticcapacitor of the present invention.

The above-described repetition of oxidative polymerization facilitatesthe production of a solid electrolyte having excellent soldering heatresistance (heat stability). In conventionally known capacitors using asolid electrolyte comprising polypyrrole or the like, the capacitorproperties greatly fluctuate at a high temperature and a high humidityand the reliability is low. In contrast, the capacitor comprising asolid electrolyte made of an electrically conducting composition of thepresent invention has excellent heat stability and exhibits goodstability in the doped state. This is because the polymer containing theabove-described organic anion as a dopant or a combination of it with adopant originated from an oxidizing agent can be deposited step by stepand thoroughly filled into the dielectric surface and even inside thepore. As a result, a capacitor having excellent heat stability such thatthe dielectric film is prevented from damages by the polymer can beprovided.

The above-described organic anion used in the present invention is adopant compound exhibiting excellent thermal stability and excellentelectrically conducting state stability in the formation of a chargetransfer complex with a π-conjugated polymer as compared withconventionally known dopants (e.g., ClO₄ ⁻, BF₄ ⁻, Cl⁻, SO₄ ²⁻, benzenesulfonate anion, alkyl-substituted naphthalene sulfonate anion, etc.).As a result, it is understood, high-performance capacitor propertiesfavored with low impedance properties and excellent heat resistance andsuperior durability in the sparking voltage test or the like areobtained.

Then, an organic anion used in the present invention is described asfollows.

(1) Alkoxy-substituted Naphthalenemonosulfonate Anion

The alkoxy-substituted naphthalenemonosulfonic acid used in the presentinvention is a generic term of alkoxy-substitutednaphthalenemonosulfonic acid compounds and other substitutednaphthalenemonosulfonic acid compounds, in which one sulfonic acid groupis substituted to the naphthalene skeleton. The compound is preferably acompound where at least one hydrogen on the naphthalene ring of anaphthalenemonosulfonic acid is substituted by a linear or branched,saturated or unsaturated alkoxy group having from 1 to 12, preferably 1to 6 carbon atoms.

Specific examples of the compound capable of providing theabove-described alkoxy-substituted naphthalene monosulfonate anionincludes a compound having a chemical structure such that the compoundskeleton is naphthalene-1-sulfonic acid, naphthalene-2-sulfonic acid oran alkali metal salt, ammonium salt or organic quaternary ammonium saltthereof and at least one hydrogen of the naphthalene ring is substitutedby an alkoxy group. That is, the compound is substituted by a linear orbranched, saturated or unsaturated alkoxy group having from 1 to 12carbon atoms, and useful examples of the substituent group includemethoxy, ethoxy, vinyloxy, propyloxy, allyloxy, isopropyloxy, butyloxy,1-butenyloxy, pentyloxy, hexyloxy, octyloxy, nonyloxy and decyloxy. Analkoxy group having a cyclic hydrocarbon moiety, such as cyclohexyloxyand phenoxy, may also be used.

Useful examples of the alkoxy-substituted naphthalenemonosulfonic acidcompound include a monosulfonic acid compound having a1-alkoxynaphthalene ring substituted at any one of the 2- to 8-positionsand a monosulfonic acid compound anion having a 2-alkoxynaphthalene ringsubstituted at any one of the 1- and 3- to 8-positions. Other thanthese, the or each hydrogen on the alkoxynaphthalene ring may besubstituted by a halogen atom such as F, Cl, Br or I, a nitro group, acyano group or the like.

(2) Sulfonate Anion of the Heterocyclic Compounds (HeterocyclicSulfonate Anion)

The heterocyclic sulfonate anion which can be used in the presentinvention is a generic term of anions of a heterocyclic sulfonic acidcompound having a chemical structure where one or more sulfonic acidgroups are substituted directly or through an alkylene group to theheterocyclic ring. Preferred examples of the skeleton of theheterocyclic compound include substituted skeletons of morpholine,piperidine, piperazine, imidazole, furan, 1,4-dioxane, benzimidazole,benzothiazolylthio, benzisoxazole, benzotriazole and benzofuran.

Preferred examples of the compound capable of providing a heterocycliccompound anion to which a sulfonate anion is indirectly substitutedinclude,

in the case of morpholine skeleton compound,

1-morpholinomethanesulfonic acid,

2-morpholinoethanesulfonic acid,

3-morpholinopropanesulfonic acid,

2-methyl-2-morpholinopropanesulfonic acid,

4-morpholinobutanesulfonic acid,

5-morpholinopentanesulfonic acid,

6-morpholinohexanesulfonic acid,

7-morpholinoheptanesulfonic acid,

8-morpholinooctanesulfonic acid,

9-morpholinononanesulfonic acid,

10-morpholinodecanesulfonic acid,

12-morpholinododecanesulfonic acid and the like;

in the case of piperidine skeleton compound,

1-piperidinomethanesulfonic acid,

2-piperidinoethanesulfonic acid,

3-piperidinopropanesulfonic acid,

2-methyl-2-piperidinopropanesulfonic acid,

4-piperidinobutanesulfonic acid,

5-piperidinopentanesulfonic acid,

6-piperidinohexanesulfonic acid,

7-piperidinoheptanesulfonic acid,

8-piperidinooctanesulfonic acid,

9-piperidinononanesulfonic acid,

10-piperidinodecanesulfonic acid,

12-piperidinododecanesulfoncic acid and the like;

in the case of piperazine skeleton compound,

piperazine-1,4-bis(1-sulfomethyl),

piperazine-1,4-bis(2-sulfoethyl),

piperazine-1,4-bis(3-sulfopropyl),

piperazine-1,4-bis(4-sulfobutyl),

piperazine-1,4-bis(5-sulfopentyl),

piperazine-1,4-bis(6-sulfohexyl),

piperazine-1,4-bis(7-sulfoheptyl),

piperazine-1,4-bis(8-sulfooctyl),

piperazine-1,4-bis(9-sulfononyl),

piperazine-1,4-bis(10-sulfodecyl),

piperazine-1,4-bis(12-sulfododecyl) and the like;

in the case of imidazole skeleton compound,

1-(2-imidazolyl)methanesulfonic acid,

2-(2-imidazolyl)ethanesulfonic acid,

3-(2-imidazolyl)propanesulfonic acid,

2-methyl-2-(2-imidazolyl)propanesulfonic acid,

4-(2-imidazolyl)butanesulfonic acid,

5-(2-imidazolyl)pentanesulfonic acid,

6-(2-imidazolyl)hexanesulfonic acid,

7-(2-imidazolyl)heptanesulfonic acid,

8-(2-imidazolyl)octanesulfonic acid,

9-(2-imidazolyl)nonanesulfonic acid,

10-(2-imidazolyl)decanesulfonic acid,

12-(2-imidazolyl)decanesulfonic acid and the like;

in the case of furan skeleton compound,

1-(2-furanyl)methanesulfonic acid,

2-(2-furanyl)ethanesulfonic acid,

3-(2-furanyl)propanesulfonic acid,

2-methyl-2-(2-furanyl)propanesulfonic acid,

4-(2-furanyl)butanesulfonic acid,

5-(2-furanyl)pentanesulfonic acid,

6-(2-furanyl)hexanesulfonic acid,

7-(2-furanyl)heptanesulfonic acid,

8-(2-furanyl)octanesulfonic acid,

9-(2-furanyl)nonanesulfonic acid,

10-(2-furanyl)decanesulfonic acid,

12-(2-furanyl)dodecanesulfonic acid and the like;

in the case of 1,4-dioxane skeleton compound,

1-(1,4-dioxan-2-yl)methanesulfonic acid,

2-(1,4-dioxan-2-yl)ethanesulfonic acid,

3-(1,4-dioxan-2-yl)propanesulfonic acid,

2-methyl-2-(1,4-dioxan-2-yl)propanesulfonic acid,

4-(1,4-dioxan-2-yl)butanesulfonic acid,

5-(1,4-dioxan-2-yl)pentanesulfonic acid,

6-(1,4-dioxan-2-yl)hexanesulfonic acid,

7-(1,4-dioxan-2-yl)heptanesulfonic acid,

8-(1,4-dioxan-2-yl)octanesulfonic acid,

9-(1,4-dioxan-2-yl)nonanesulfonic acid,

10-(1,4-dioxan-2-yl)decanesulfonic acid,

12-(1,4-dioxan-2-yl)dodecanesulfonic acid and the like;

in the case of benzimidazole skeleton compound,

1-(1-benzimidazolyl)methanesulfonic acid,

2-(1-benzimidazolyl)ethanesulfonic acid,

3-(1-benzimidazolyl)propanesulfonic acid,

2-methyl-2-(1-benzimidazolyl)propanesulfonic acid,

4-(1-benzimidazolyl)butanesulfonic acid,

5-(1-benzimidazolyl)pentanesulfonic acid,

6-(1-benzimidazolyl)hexanesulfonic acid,

7-(1-benzimidazolyl)heptanesulfonic acid,

8-(1-benzimidazolyl)octanesulfonic acid,

9-(1-benzimidazolyl)nonanesulfonic acid,

10-(1-benzimidazolyl)decanesulfonic acid,

12-(1-benzimidazolyl)dodecanesulfonic acid and the like;

in the case of benzothiazolylthio skeleton compound,

1-(2-benzothiazolylthioyl)methanesulfonic acid,

2-(2-benzothiazolylthioyl)ethanesulfonic acid,

3-(2-benzothiazolylthioyl)propanesulfonic acid,

2-methyl-2-(2-benzothiazolylthioyl)propanesulfonic acid,

4-(2-benzothiazolylthioyl)butanesulfonic acid,

5-(2-benzothiazolylthioyl)pentanesulfonic acid,

6-(2-benzothiazolylthioyl)hexanesulfonic acid,

7-(2-benzothiazolylthioyl)heptanesulfonic acid,

8-(2-benzothiazolylthioyl)octanesulfonic acid,

9-(2-benzothiazolylthioyl)nonanesulfonic acid,

10-(2-benzothiazolylthioyl)decanesulfonic acid,

12-(2-benzothiazolylthioyl) dodecanesulfonic acid and the like;

in the case of benzisoxazole skeleton compound,

1-(1-benzisoxazolyl)methanesulfonic acid,

2-(1-benzisoxazolyl)ethanesulfonic acid,

3-(1-benzisoxazolyl)propanesulfonic acid,

2-methyl-2-(1-benzisoxazolyl)propanesulfonic acid,

4-(1-benzisoxazolyl)butanesulfonic acid,

5-(1-benzisoxazolyl)pentanesulfonic acid,

6-(1-benzisoxazolyl)hexanesulfonic acid,

7-(1-benzisoxazolyl)heptanesulfonic acid,

8-(1-benzisoxazolyl)octanesulfonic acid,

9-(1-benzisoxazolyl)nonanesulfonic acid,

10-(1-benzisoxazolyl)decanesulfonic acid,

12-(1-benzisoxazolyl)dodecanesulfonic acid and the like;

in the case of benzotriazole skeleton compound,

1-(2-benzotriazolyl)methanesulfonic acid,

2-(2-benzotriazolyl)ethanesulfonic acid,

3-(2-benzotriazolyl)propanesulfonic acid,

2-methyl-2-(2-benzotriazolyl)propanesulfonic acid,

4-(2-benzotriazolyl)butanesulfonic acid,

5-(2-benzotriazolyl)pentanesulfonic acid,

6-(2-benzotriazolyl)hexanesulfonic acid,

7-(2-benzotriazolyl)heptanesulfonic acid,

8-(2-benzotriazolyl)octanesulfonic acid,

9-(2-benzotriazolyl)nonanesulfonic acid,

10-(2-benzotriazolyl)decanesulfonic acid,

12-(2-benzotriazolyl)dodecanesulfonic acid and the like; and

in the case of benzofuran skeleton compound,

1-(3-benzofuranyl)methanesulfonic acid,

2-(3-benzofuranyl)ethanesulfonic acid,

3-(3-benzofuranyl) propanesulfonic acid,

2-methyl-2-(3-benzofuranyl)propanesulfonic acid,

4-(3-benzofuranyl)butanesulfonic acid,

5-(3-benzofuranyl)pentanesulfonic acid,

6-(3-benzofuranyl)hexanesulfonic acid,

7-(3-benzofuranyl)heptanesulfonic acid,

8-(3-benzofuranyl)octanesulfonic acid,

9-(3-benzofuranyl)nonanesulfonic acid,

10-(3-benzofuranyl)decanesulfonic acid,

12-(3-benzofuranyl)dodecanesulfonic acid and the like.

These sulfonic acid compounds as the compound capable of providing theanion may also be preferably used in the form of an alkali metal saltsuch as sodium salt or potassium salt, or a quaternary nitrogen-typecompound salt such as ammonium salt.

Specific preferred examples of the heterocyclic compound where thesulfonic acid group is directly substituted to the heterocyclic skeletoninclude 2-imidazolesulfonic acid, furan-2-sulfonic acid,furan-3-sulfonic acid, 2-benzimidazolesulfonic acid,benzofuran-3-sulfonic acid, and an alkali metal salt such as sodiumsalt, an ammonium salt and a quaternary ammonium salt thereof.

The heterocyclic sulfonate anion may also be preferably in the form of aderivative where at least one hydrogen of the heterocyclic skeleton issubstituted by a linear or branched, saturated or unsaturated alkylgroup having from 1 to 12 carbon atoms, preferably from 1 to 6 carbonatoms.

Specific examples of the substituent include an alkyl group such as amethyl group, an ethyl group, a propyl group, an isopropyl group, abutyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexylgroup, an octyl group, a decyl group and a dodecyl group; an unsaturatedgroup such as a vinyl group, an allyl group, a 3-butenyl group and a5-hexenyl group; a methoxy group, an ethoxy group, a propyloxy group, abutyloxy group, a pentyloxy group, a hexyloxy group, an octyloxy group,a decyloxy group and a dodecyloxy group.

(3) Anion of a Aliphatic Polycyclic Compound

The anion of aliphatic polycyclic compound for use in the presentinvention is a compound having a dicyclic or more polycyclic aliphaticanion containing a group of BrØnsted acid such as sulfonic acid,carboxylic acid, phosphoric acid or boric acid, preferably a compoundsubstituted with sulfonic acid or carboxylic acid, more preferably asulfonic acid-substituted compound. Useful examples thereof included-camphor sulfonic acid (XVII) (another name: 10-camphor sulfonic acid),2-camphor sulfonic acid (XVIII), 3-camphor sulfonic acid, 8-camphorsulfonic acid, d-camphor carboxylic acid and derivatives thereof. Theycan be used in the form of ammonium salt or alkali metal salt.

The oxidizing agent for use in the present invention may be anyoxidizing agent suitable for the oxidation polymerization of pyrroles orthiophenes. Examples of the oxidizing agent which can used includeoxidizing agents over a wide range, such as iron(III) chloride,Fe(ClO₄)₃, organic acid iron(III), inorganic acid iron(III), alkylpersulfate, ammonium persulfate, hydrogen peroxide and K₂Cr₂O₇ describedin JP-A-2-15611. Examples of the organic acid of the organic acidiron(III) include an alkylsulfonic acid (or alkanesulfonic acid) havingfrom 1 to 20 carbon atoms such as methanesulfonic acid anddodecylbenzenesulfonic acid, and an aliphatic carboxylic acid havingfrom 1 to 20 carbon atoms. In the strict meaning, the kind of theoxidizing agent that can be used may be restricted by the chemicalstructure of the polymerizable monomer compound represented by generalformula (III), the oxidizing agent, reaction conditions and the like.

For example, according to Handbook of Conducting Polymers, page 99, FIG.5, Marcel Dekker, Inc. (1987), the species of the substituent greatlyaffects the oxidation potential (one index for showing whether thepolymerization readily or difficultly occurs) and in turn, governs theoxidation (polymerization) of thiophenes (oxidation potential expandsover a wide range of from about 1.8 to about 2.7 V). Accordingly, to bemore concrete, the combination of the polymerizable monomer compound andthe oxidizing agent used and reaction condition is important.

The dopant other than the above-described organic anion may be onederived from a reductant anion after the reaction of the oxidizingagent. Specific examples thereof include chloride ion, ClO₄ ⁻, aliphaticorganic carboxylate anion having from 1 to 12 carbon atoms, sulfate ion,phosphate anion, aliphatic organophosphate anion having from 1 to 12carbon atoms and borate anion. Furthermore, an electron acceptor dopantsuch as NO⁺ and NO₂ ⁺ salts (e.g., NOBF₄, NOPF₆, NOSbF₆, NOAsF₆,NOCH₃SO₃, NO₂BF₄, NO₂PF₆, NO₂CF₃SO₃) may also be used.

In the manufacturing method of a solid electrolytic capacitor of thepresent invention, the chemical polymerization of a thiophene monomercompound represented by general formula (IV) is particularly preferablyperformed using a persulfate oxidizing agent. On the other hand, the useof iron (III) salt-based oxidizing agent is not preferable in that aniron element remains in the electrically conducting polymer compositionand adversely affects the capacitor properties. Persulfates suitable forthe polymerizable monomer compound represented by formula (IV) are,however, not suitable for the thiophene (R¹=R²=H, X=S) monomer compoundrepresented by general formula (III), and thus the use of persulfates islimited and use as an oxidizing agent may be prohibited depending on thekind of monomer. Examples of the persulfate which can be particularlysuitably used for the chemical polymerization of a thiophene representedby general formula (IV) include ammonium persulfate and potassiumpersulfate.

Preferred conditions for the production (polymerization) reaction aredescribed below.

Respective concentrations of the polymerizable monomer compoundrepresented by formula (III) or (IV), the oxidizing agent and theabove-described organic anion dopant in any one of (1) to (3) above usedin the manufacturing method of a capacitor of the present invention varydepending on the kind of the monomer compound, substituents thereod andthe combination with a solvent or the like. However, it is in generalfrom 1×10⁻⁴ to 10 mol/l, preferably from 1×10⁻³ to 5 mol/l. The reactiontemperature varies depending on the kind of reaction methods and cannotbe specifically limited. However, the reaction proceeds generally from−70 to 250° C., preferably from 0 to 150° C. and more preferably from 15to 100° C.

Examples of the solution for use in the manufacturing method of thepresent invention or the solvent for use in washing after thepolymerization include ethers such as tetrahydrofuran (THF), dioxane,diethyl ether, ketones such as acetone and methyl ethyl ketone, aproticpolar solvents such as dimethylformamide, acetonitrile, benzonitrile,N-methylpyrrolidone (NMP) and dimethylsulfoxide (DMSO), esters such asethyl acetate and butyl acetate, nonaromatic chlorine-based solventssuch as chloroform and methylene chloride, nitro compounds such asnitromethane, nitroethane and nitrobenzene, alcohols such as methanol,ethanol and propanol, organic acids such as formic acid, acetic acid andpropionic acid, acid anhydrides of the organic acid (e.g., aceticanhydride), water, and mixed solvents thereof. Of these, preferred arewater, an alcohol, a ketone and/or a combination system thereof.

The outline of the solid electrolytic capacitor of the present inventionis described below by referring to FIG. 1.

For one part electrode (anode) 1 having formed on the entire surfacethereof pores 2, connected to a connecting lead 7, a known material maybe used, for example, a metal foil or bar having a valve action such asaluminum, titanium, tantalum, niobium or an alloy using such a metal asa base, or a sintered body mainly comprising such a metal may be used.This metal electrode is used after etching or forming the surfacethereof by a known method and then forming a metal oxide film layer 3 onthe metal foil so as to form a dielectric material layer and increasethe specific surface area.

The solid electrolyte (electrically conducting polymer composition) 4 ispreferably produced by a method of polymerizing a monomer compound onthe dielectric layer, more preferably by a method of chemicallydepositing an electrically conducting polymer composition havingexcellent heat resistance of the present invention on a dielectricmaterial having a porous or void structure.

On the thus-produced electrically conducting composition layer, anotherelectric conductor layer is preferably provided so as to attain betterelectrical contacting. The electric conductor layer 5 is formed, forexample, by applying an electrically conducting paste, plating,metallization or formation of an electrically conducting resin film.

The solid electrolytic capacitor thus manufactured according to themanufacturing method of the present invention is covered with a jacket 6by means of resin molding on the electric conductor layer, a resin case,a metal-made jacket case or resin dipping and then a connecting lead 7is provided thereto. Thus, a solid electrolytic capacitor as a finalproduct suitable for various uses can be obtained.

Best Mode for Carrying Out the Invention

Hereafter, the present invention will be described by examples,comparative examples and reference examples. However, the presentinvention should by no means be construed as being limited thereby.

EXAMPLE 1

A formed aluminum foil was processed to have a prescribed area and thensubjected to forming at 13 V in an aqueous 10 wt % ammonium adipatesolution to prepare a dielectric material on the aluminum foil. Thesurface of this dielectric material was dipped in an aqueous solutionprepared to have an ammonium persulfate (hereinafter simply referred toas “APS”) concentration of 20 wt % and a sodium2-propyloxynaphthalene-6-sulfonate concentration of 0.3 wt % (Solution3), and then the dielectric foil was dipped in 1.2 mol/l of anisopropanol (hereinafter simply referred to as “IPA”solution havingdissolved therein 5 g of 3,4-dioxyethylene-thiophene (Solution 4). Theresulting substrate was taken out and left standing in an environment at60° C. for 10 minutes, thereby completing the oxidative polymerization,and then the substrate was washed with water. This polymerizationreaction and the washing each was repeated 10 times. The polymerizationproduct was reduced with hydrazine in a water/IPA solvent and thencarefully extracted and the contents of sulfate ion and2-propyloxynaphthalene-6-sulfonate ion in the polymerization productwere determined by an ion chromatography method. As a result, thesulfate ion content was 1.6 mol % and the2-propyloxynaphthalene-6-sulfonate ion content was 13.6 mol %, per allthe repeating structural units of the polymer. The solid electrolytelayer had an electric conductivity of 75 S/cm.

Thereafter, the aluminum foil having deposited thereon polythiophenepolymerization product was treated in an aqueous 10 wt % ammoniumadipate solution and then examined on the sparking voltage. The test wasperformed by increasing the number of devices so as to attaindistinguished comparison of the device properties (the same applies tothe following Examples), more specifically, in an environment of 50° C.under the conditions of a current density of 10 mA/cm² with the numberof device being n=5 times. The results obtained are shown in Table 1.Subsequently, the aluminum core part was welded with a plus side leadfor collecting the current from the anode and on the other hand,connected to the minus side lead through carbon paste and silver pastefor collecting the current from the cathode. These elements were finallysealed by an epoxy resin to manufacture a capacitor device. Thecapacitor device manufactured was aged at 125° C. for 2 hours and thensubjected to the initial evaluation. The results obtained are showntogether in Table 2. In the Table, C in the column of initialcharacteristics indicates a capacitance and DF indicates a tangent ofthe loss angle (tan δ). These were each measured at 120 Hz. Theimpedance is shown by a value at a resonance frequency. LC (leakagecurrent) was measured one minute after a rated voltage was applied. Themeasured values each is an average of 30 samples. With respect to LC,those having an LC of 1 μA or more are judged as a defective and thosehaving an LC of 10 μA or more are judged as a shorted product. Theaverage LC is calculated exclusive of the defective units.

EXAMPLE 2

The surface of a dielectric material prepared in the method described inExample 1 was impregnated with an aqueous solution prepared to have anAPS concentration of 20 wt % (Solution 1) and then dipped in anIPA/water mixed solution prepared by adding tetrabutylammonium2-propyloxynaphthalene-6-sulfonate to 1.2 mol/l of an IPA solutionhaving dissolved therein 5 g of 3,4-dioxyethylenethiophene to have atetrabutylammonium 2-propyloxynaphthalene-6-sulfonate concentration of0.1 wt % (Solution 2). The tetrabutylammonium2-propyloxynaphthalene-6-sulfonate used here was one obtained by therecrystallization after mixing and reacting sodium2-propyloxynaphthalene-6-sulfonate with tetrabutylammonium bromide. Theresulting substrate was taken out and left standing in an environment at60° C. for 10 minutes, thereby completing the oxidative polymerization,and then the substrate was washed with water. This polymerizationreaction and the washing each was repeated 10 times. The capacitordevice obtained was evaluated. The results are shown in Tables 1 and 2.The contents of sulfate ion and 2-propyloxynaphthalene-6-sulfonate ionin the polymerization product were determined according to the methoddescribed in Example 1. As a result, the sulfate ion content was 2.2 mol% and the 2-propyloxynaphthalene-6-sulfonate ion content was 7.5 mol %.The solid electrolyte layer had an electric conductivity of 58 S/cm.

EXAMPLE 3

A dielectric material prepared by the method described in Example 1 wasdipped in 1.2 mol/l of an IPA solution having dissolved therein 5 g of3,4-dioxyethylene-thiophene (Solution 4) and then dipped in an aqueoussolution prepared to have an APS concentration of 20 wt % and a sodium2-methoxynaphthalene-6-sulfonate concentration of 0.1 wt % (Solution 3).The resulting substrate was taken out and left standing in anenvironment at 60° C. for 10 minutes, thereby completing the oxidativepolymerization, and then the substrate was washed with water. Thispolymerization reaction and the washing each was repeated 10 times. Thecapacitor device obtained was evaluated and the results obtained areshown in Tables 1 and 2. The contents of sulfate ion and2-methoxynaphthalene-6-sulfonate ion in the polymerization product weredetermined according to the method described in Example 1. As a result,the sulfate ion content was 1.8 mol % and the2-methoxynaphthalene-6-sulfonate ion content was 0.8 mol %. The solidelectrolyte layer had an electric conductivity of 60 S/cm.

EXAMPLE 4

A dielectric material was prepared by the method described in Example 1.The surface of this dielectric material was dipped in an aqueoussolution prepared to have a potassium persulfate concentration of 10 wt% and a sodium 2-methoxynaphthalene-6-sulfonate concentration of 0.1 wt% (Solution 3) and then dipped in 1.2 mol/l of an IPA solution havingdissolved therein 5 g of 3,4-dioxyethylene-thiophene (Solution 4). Theresulting substrate was taken out and left standing in an environment at60° C. for 10 minutes, thereby completing the oxidative polymerization.This dipping process was repeated 10 times, and then the substrate waswashed with water and dried. The capacitor device obtained was evaluatedand the results obtained are shown in Tables 1 and 2. The contents ofsulfate ion and 2-methoxynaphthalene-1-sulfonate ion in thepolymerization product were determined according to the method describedin Example 1. As a result, the sulfate ion content was 5.9 mol % and the2-methoxynaphthalene-6-sulfonate ion content was 15.5 mol %. The solidelectrolyte layer had an electric conductivity of 73 S/cm.

EXAMPLE 5

A dielectric material was prepared by the method described in Example 1.The surface of this dielectric material was dipped in an aqueoussolution prepared to have an APS concentration of 35 wt % (Solution 1)and then dipped in an IPA/water mixed solution having antetrabutylammonium 2,3-dimethoxynaphthalene-6-sulfonate concentration of0.04 wt % (Solution 2) prepared by adding tetrabutylammonium2,3-dimethylnaphthalene-6-sulfonate to 1.2 mol/l of an IPA solutionhaving dissolved therein 5 g of 3,4-dioxyethylene-thiophene. At thistime, the tetrabutylammonium 2,3-dimethoxynaphthalene-6-sulfonate usedwas one obtained by the recrystallization after mixing and reactingsodium 2,3-dimethoxynaphthalene-6-sulfonate with tetrabutylammoniumbromide.

The resulting substrate was taken out and left standing in anenvironment at 60° C. for 10 minutes, thereby completing the oxidativepolymerization. This dipping process was repeated 10 times and then thesubstrate was washed with water and dried. The capacitor device obtainedwas evaluated and the results obtained are shown in Tables 1 and 2. Thecontents of sulfate ion and 2,3-dimethoxynaphthalene-6-sulfonate ion inthe polymerization product were determined according to the methoddescribed in Example 1. As a result, the sulfate ion content was 5.2 mol% and the 2,3-dimethoxynaphthalene-6-sulfonate ion content was 7.8 mol%. The solid electrolyte layer had an electric conductivity of 40 S/cm.

EXAMPLE 6

A dielectric material was prepared by the method described in Example 1.This dielectric material was dipped in a degassed IPA solution of5,6-dimethoxyisothianaphthene in a concentration of 1.2 mol/lsynthesized and produced by sublimation according to the methoddescribed in JP-A-2-242816 (Solution 4) and then dipped in an aqueoussolution prepared by adding sodium 2-propyloxynaphthalene-6-sulfonate toan APS aqueous solution having a concentration of 20 wt % and adjustedto have a sodium 2-propyloxynaphthalene-6-sulfonate concentration of 0.1wt % (Solution 3). The resulting substrate was taken out and leftstanding in an environment at 60° C. for 10 minutes, thereby completingthe oxidative polymerization. This dipping process was repeated 10 timesand then the substrate was washed with water and dried. The capacitordevice obtained was evaluated and the results obtained are shown inTables 1 and 2. The contents of sulfate ion and2-propyloxynaphthalene-6-sulfonate ion in the polymerization productwere determined according to the method described in Example 1. As aresult, the sulfate ion content was 0.7 mol % and the2-propyloxynaphthalene-6-sulfonate ion content was 6.0 mol %. The solidelectrolyte layer had an electric conductivity of 33 S/cm.

EXAMPLE 7

A capacitor device was prepared and evaluated in the same manner as inExample 1 except for using a solution of N-methylpyrrole prepared tohave the same concentration in place of 3,4-dioxyethylenethiophene usedin Example 1. The results obtained are shown in Tables 1 and 2. Thecontents of sulfate ion and 2-methoxynaphthalene-6-sulfonate ion in thepolymerization product were determined according to the method describedin Example 1. As a result, the sulfate ion content was 7.8 mol % and the2-methoxynaphthalene-6-sulfonate ion content was 12.3 mol %. The solidelectrolyte layer had an electric conductivity of 7 S/cm.

EXAMPLE 8

A formed aluminum foil was processed to have a prescribed area and thensubjected to forming at 13 V in an aqueous 10 wt % ammonium adipatesolution to prepare a dielectric material. This dielectric material wasdipped in a 30% DMF-IPA solution prepared to have a sodium2-methoxynaphthalene-6-sulfonate concentration of 0.1 wt % and a3,4-dioxyethylenethiophene concentration of 1.2 mol/l (Solution 2) andthen dipped in a 20 wt % aqueous APS solution (Solution 1). Theresulting substrate was taken out and left standing in an environment at60° C. for 10 minutes, thereby completing the oxidative polymerization.This dipping process was repeated 10 times and then the substrate waswashed with water and dried. The capacitor device obtained was evaluatedand the results obtained are shown in Tables 1 and 2. The sulfate ioncontent was 1.5 mol % and the 2-methoxynaphthalene-6-sulfonate ioncontent was 3.2 mol %, per all repeating structural units of thepolymer. The solid electrolyte layer had an electric conductivity of 71S/cm.

EXAMPLE 9

A capacitor device was prepared and evaluated in the same manner as inExample 1 except for changing the 20 wt % APS used in Example 1 to 12 wt% APS. The results are shown in Tables 1 and 2. The contents of sulfateion and 2-methoxynaphthalene-6-sulfonate ion in the polymerizationproduct were determined according to the method described in Example 1.As a result, the sulfate ion content was 0.2 mol % and the2-methoxynaphthalene-6-sulfonate ion content was 20 mol %. The solidelectrolyte layer had an electric conductivity of 28 S/cm.

EXAMPLE 10

A formed dielectric material was prepared in the same manner as inExample 1 and the dielectric material obtained was dipped in a 12% IPAsolution of ferric 2-methoxynaphthalene-6-sulfonate and then dipped in1.2 mol/l of an IPA solution having dissolved therein 5 g of3,4-dioxyethylenethiophene. The resulting substrate was left standing inan environment at 60° C. for 10 minutes, thereby completing theoxidative polymerization, and then the substrate was washed with water.This polymerization reaction and the washing each was repeated 10 times.The polymerization product was reduced with hydrazine in a water/IPAsolvent and then carefully extracted and the content of2-methoxynaphthalene-6-sulfonate ion in the polymerization product wasdetermined by an ion chromatography method. As a result, the2-methoxynaphthalene-6-sulfonate ion content was 17 mol % per the totalrepeating structural unit of the polymer. The solid electrolyte layerhad an electric conductivity of 30 S/cm. Thereafter, a capacitor devicewas manufactured and examined on the sparking voltage and othercapacitor properties in the same manner as in Example 1. The resultsobtained are shown in Tables 1 and 2.

EXAMPLE 11

A capacitor device was prepared and evaluated in the same manner as inExample 1 except for using a solution prepared to have a ferric sulfateconcentration of 10 wt % in place of APS used in Example 1 and a sodium2-methoxynaphthalene-6-sulfonate concentration of 0.1 wt %. The resultsobtained are shown in Tables 1 and 2. The contents of sulfate ion and2-methoxy-naphthalene-6-sulfonate ion in the polymerization product weredetermined according to the method described in Example 1. As a result,the sulfate ion content was 24.5 mol % and the2-methoxynaphthalene-6-sulfonate ion content was 33.8 mol %. However,the capacitor properties were poor because 8 mol % of iron ion waspresent and the sulfate ion content exceeded 10 mol %.

EXAMPLE 12

A capacitor device was prepared and evaluated in the same manner as inExample 1 except for using thiophene in place of3,4-dioxyethylenethiophene used in Example 1 and using a solutionprepared to have a ferric chloride concentration of 10 wt % in place ofAPS and a sodium 2-methoxynaphthalene-6-sulfonate concentration of 0.1wt %. The results obtained are shown in Tables 1 and 2. The2-methoxynaphthalene-6-sulfonate ion content in the polymerizationproduct was determined according to the method described in Example 1and found to be 3.1 mol %. Since sulfate ion was not contained incombination, the capacitor properties were poor.

Reference Example 1

Manufacture of a capacitor device was attempted under the sameconditions as in Example 1 except for using thiophene in place of 3,4-dioxyethylenethiophene used in Example 1. However, black bluepolythiophene polymer was not produced at all, thus the polymerizationof thiophene was not generated by the action of APS. In other words,oxidative polymerization of thiophenes by APS was peculiar to 3,4-dioxygroup-substituted thiophenes.

Reference Example 2

A capacitor device was prepared and evaluated in the same manner as inExample 1 except for using sodium 2-hydroxynaphthalene-6-sulfonate inplace of sodium 2-propyloxynaphthalene-6-sulfonate used in Example 1.The results are shown in Tables 1 and 2. The contents of sulfate ion and2-hydroxynaphthalene-6-sulfonate ion were determined according to themethod described in Example 1. As a result, the sulfate ion content was4.3 mol % and the 2-hydroxynaphthalene-6-sulfonate ion content was 12.1mol %. The solid electrolyte layer had an electric conductivity of 10S/cm.

In the sparking voltage test of Examples 1 to 9, the voltage wasscarcely reduced and the dielectric film was not damaged in any case.However, in the sparking voltage test of Examples 10 to 12, although thevoltage was not reduced in the capacitor using an organic iron salt ofExample 10, capacitors using an inorganic iron salt underwent greatreduction in the voltage and in any case, failed in holding the voltageuntil the test was repeated prescribed times. In particular, in thecapacitor using iron sulfate of Example 11, the sparking voltage wasgreatly reduced due to iron ion remaining in a concentration as high as8 mol % and the sparking voltage decreased by the dipping steps ofseveral times, as a result, the dielectric layer was disadvantageouslydamaged.

TABLE 1 Sparking Voltage (unit: V, Device Number n = 5) Number ofPolymerization Operations 1 2 3 4 5 6 8 10 Example 1 19 19 19 19 19 1919 19 Example 2 19 19 19 19 19 19 19 19 Example 3 19 19 19 19 19 19 1919 Example 4 19 19 19 18 17 16 15 11 Example 5 19 19 19 19 19 19 19 19Example 6 19 19 19 19 19 19 19 19 Example 7 19 19 19 19 19 19 19 19Example 8 19 19 19 19 19 19 19 19 Example 9 19 19 19 19 19 19 19 19Example 10 19 19 19 19 19 19 19 19 Example 11 19 16 14  7  3 Example 1218 16 10  3 Reference 19 18 15 11  9  3 Example 2

TABLE 2 Initial Characteristics C DF Z LC Defective/Sample Short μF % mΩμA units/units Circuit Example 1 8.1 0.8 60 0.02 0/30 0 Example 2 8.00.8 60 0.02 0/30 0 Example 3 7.6 0.8 60 0.02 0/30 0 Example 4 7.0 0.8 600.04 1/30 0 Example 5 6.8 0.9 60 0.05 1/30 0 Example 6 6.8 0.8 60 0.051/30 0 Example 7 4.0 1.3 60 0.11 1/30 0 Example 8 8.2 0.7 60 0.02 0/30 0Example 9 6.9 0.7 60 0.10 1/30 0 Example 10 6.9 1.0 60 0.10 1/30 0Example 11 6.1 3.2 83 0.41 15/30  10  Example 12 5.9 3.0 87 0.40 27/30 16  Reference 5.0 1.2 60 0.10 3/30 0 Example 2

EXAMPLE 13

A formed aluminum foil was processed to have a prescribed area and thensubjected to forming at 13 V in an aqueous 10 wt % ammonium adipatesolution to form a dielectric layer on the foil surface. This formedaluminum foil (substrate) was dipped in an aqueous solution prepared soas to have an APS concentration of 20 wt % and a sodium4-morpholinepropanesulfonate (produced by Tokyo Kasei) concentration of0.125 wt % (Solution 3) and then dipped in 1.2 mol/l of an IPA solutionhaving dissolved therein 5 g of 3,4-dioxyethylenethiophene (Solution 4).

The resulting substrate was taken out and left standing in anenvironment at 60° C. for 10 minutes, thereby completing the oxidativepolymerization, and then the substrate was washed with water. Thispolymerization reaction and the washing each was repeated 10 times.

The substrate after the polymerization was reduced with hydrazine in awater/IPA solvent and then carefully extracted and the contents ofsulfate ion and 4-morpholinepropanesulfonate ion in the electricallyconducting polymer composition were determined by an ion chromatographymethod. As a result, the sulfate ion content was 1.5 mol % and the4-morpholinepropanesulfonate ion content was 14.0 mol %, per allrepeating structural units of the polymer in the electrically conductingpolymer composition. The solid electrolyte layer had an electricconductivity of 73 S/cm.

Thereafter, the aluminum foil substrate having deposited thereonpoly-3,4-dioxyethylenethiophene polymer composition was treated in anaqueous 10 wt % ammonium adipate solution and then examined on thesparking voltage. The test was performed by increasing the number ofdevices so as to attain distinguished comparison of the deviceproperties (the same applies to the following Examples), morespecifically, in an environment of 50° C. under the conditions of acurrent density of 10 mA/cm² and n=5 times. The results obtained areshown in Table 3.

Subsequently, the aluminum core part was welded with a plus side leadfor collecting the current from the anode of the solid electrolyticcapacitor and also connected to the minus side lead through carbon pasteand silver paste for collecting the current from the cathode. Theseelements were finally sealed by an epoxy resin to manufacture acapacitor device. The capacitor device manufactured was aged at 125° C.for 2 hours and then subjected to the initial evaluation. The resultsobtained are shown together in Table 4.

In the Table 4, C in the column of initial characteristics indicates acapacitance and DF indicates a tangent of the loss angle (tan δ). Thesewere each measured at 120 Hz. The impedance is shown by a value at aresonance frequency. LC (leakage current) was measured one minute aftera rated voltage was applied. The measured values each is an average of30 samples. With respect to LC, those having an LC of 1 μA or more arejudged as a defective and those having an LC of 10 μA or more are judgedas a shorted product. The average LC is calculated exclusive of thesedefective units.

EXAMPLE 14

The surface of a dielectric material prepared in the method described inExample 13 was impregnated with an aqueous solution prepared to have anAPS concentration of 20 wt % (Solution 1) and then dipped in anIPA/water mixed solution prepared by adding tetrabutylammonium4-morpholinepropanesulfonate (hereinafter simply referred to as“MOPSTB”) to 1.2 mol/l of an IPA solution having dissolved therein 5 gof 3,4-dioxyethylenethiophene to have tetrabutylammonium4-morpholinepropanesulfonate concentration of 0.1 wt % (Solution 2). TheMOPSTB salt used here was one obtained by the recrystallization fromsodium 4-morpholinepropanesulfonate (produced by Tokyo Kasei) aftermixing and reacting it with tetrabutylammonium bromide. The resultingsubstrate was taken out and left standing in an environment at 60° C.for 10 minutes, thereby completing the oxidative polymerization, andthen the substrate was washed with water. This polymerization reactionand the washing each was repeated 10 times. The capacitor deviceobtained was evaluated. The measurement was performed in the same manneras in Example 13 and the results are shown in Tables 3 and 4.

The contents of sulfate ion and 4-morpholinepropanesulfonate ion in thepolymer composition were determined according to the method described inExample 13. As a result, the sulfate ion content was 1.6 mol % and the4-morpholinepropanesulfonate ion content was 8.1 mol %. The solidelectrolyte layer had an electric conductivity of 56 S/cm.

EXAMPLE 15

A formed aluminum foil having produced thereon a dielectric materialprepared in the same manner in Example 13 was dipped in 1.2 mol/l of anIPA solution having dissolved therein 5 g of 3,4-dioxyethylenethiophene(Solution 4) and then dipped in an aqueous solution prepared to have anAPS concentration of 20 wt % and a sodium 4-morpholinepropanesulfonateconcentration of 0.1 wt % (Solution 3). The resulting substrate wastaken out and left standing in an environment at 60° C. for 10 minutes,thereby completing the oxidative polymerization, and then the substratewas washed with water.

This polymerization reaction and the washing each was repeated 10 times.The capacitor device obtained was evaluated in the same manner as inExample 13 and the results obtained are shown in Tables 3 and 4.

The contents of sulfate ion and 4-morpholinepropanesulfonate ion in thepolymer composition were determined according to the method described inExample 13. As a result, the sulfate ion content was 2.0 mol % and the4-morpholinepropanesulfonate ion content was 0.6 mol %. The solidelectrolyte layer had an electric conductivity of 60 S/cm.

EXAMPLE 16

A formed aluminum foil having produced thereon a dielectric materialprepared in the same manner as in Example 13 was dipped in 1.2 mol/l ofan IPA solution having dissolved therein 5 g of3,4-dioxyethylenethiophene (Solution 4) and then dipped in an aqueoussolution prepared to have an APS concentration of 20 wt % and a sodium4-morpholinepropanesulfonate concentration of 0.3 wt % (Solution 3). Theresulting substrate was taken out and left standing in an environment at60° C. for 10 minutes, thereby completing the oxidative polymerization,and then the substrate was washed with water.

The polymerization reaction and the washing each was repeated 10 times.The capacitor device obtained was evaluated in the same manner as inExample 13 and the results are shown in Tables 3 and 4.

The contents of sulfate ion and 4-morpholineethanesulfonate ion in thepolymer composition were determined according to the method described inExample 13. As a result, the sulfate ion content was 2.1 mol % and the4-morpholineethanesulfonate ion content was 0.8 mol %. The solidelectrolyte layer had an electric conductivity of 68 S/cm.

EXAMPLE 17

A formed aluminum foil having produced thereon a dielectric material wasprepared in the same manner as in Example 13. The surface of thisdielectric material was impregnated with an aqueous solution prepared tohave a potassium persulfate concentration of 10 wt % and a sodium4-morholinepropanesulfonate (Tokyo Kasei) concentration of 0.1 wt %(Solution 3) and then dipped in 1.2 mol/l of an IPA solution havingdissolved therein 5 g of 3,4-dioxyethylenethiophene. The resultingsubstrate was taken out and left standing in an environment at 60° C.for 10 minutes, thereby completing the oxidative polymerization. Thisdipping process was repeated 10 times and then the substrate was washedwith water and dried. The capacitor device obtained was evaluated in thesame manner as in Example 13 and the results are shown in Tables 3 and4.

The contents of sulfate ion and 4-morpholinepropanesulfonate ion in thepolymer composition were determined according to the method described inExample 13. As a result, the sulfate ion content was 6.2 mol % and the4-morpholinepropanesulfonate ion content was 15 mol %. The solidelectrolyte layer had an electric conductivity of 74 S/cm.

EXAMPLE 18

A formed aluminum foil having produced thereon a dielectric material wasprepared in the same manner as in Example 13. This formed aluminum foilwas dipped in a degassed IPA solution of 5,6-dimethoxyisothianaphthenein a concentration of 1.2 mol/l synthesized and produced by sublimationaccording to the method described in JP-A-2-242816 (Solution 4) and thendipped in an aqueous solution prepared by adding sodium4-morpholinepropanesulfonate to an APS aqueous solution having aconcentration of 20 wt and adjusted to have a sodium4-morpholinepropanesulfonate concentration of 0.1 wt % (Solution 3). Theresulting substrate was taken out and left standing in an environment at60° C. for 10 minutes, thereby completing the oxidative polymerization.This dipping process was repeated 10 times and then the substrate waswashed with water and dried. The capacitor device obtained was evaluatedin the same manner as in Example 13 and the results are shown in Tables3 and 4.

The contents of sulfate ion and 4-morpholinepropanesulfonate ion in thepolymer composition were determined according to the method described inExample 13. As a result, the sulfate ion content was 0.8 mol % and the4-morpholinepropanesulfonate ion content was 5.7 mol %. The solidelectrolyte layer had an electric conductivity of 31 S/cm.

EXAMPLE 19

A capacitor device was prepared and evaluated in the same manner as inExample 13 except for using a solution of N-methylpyrrole prepared tohave the same concentration in place of 3,4-dioxyethylenethiophene usedin Example 13. The results obtained are shown in Tables 3 and 4.

The contents of sulfate ion and 4-morpholinepropanesulfonate ion in thepolymer composition were determined according to the method described inExample 13. As a result, the sulfate ion content was 6.8 mol % and the4-morpholinepropanesulfonate ion content was 16.8 mol %. The solidelectrolyte layer had an electric conductivity of 7 S/cm.

EXAMPLE 20

A formed aluminum foil was processed to have a prescribed area and thensubjected to forming at 13 V in an aqueous 10 wt % ammonium adipatesolution to prepare a dielectric material. This dielectric material wasdipped in a 30% DMF-IPA solution prepared to have a sodium4-morpholinepropanesulfonate concentration of 0.1 wt % and a3,4-dioxyethylenethiophene concentration of 1.2 mol/l (Solution 2) andthen dipped in a 20 wt % aqueous APS solution (Solution 1). Theresulting substrate was taken out and left standing in an environment at60° C. for 10 minutes, thereby completing the oxidative polymerization.This dipping process was repeated 10 times and then the substrate waswashed with water and dried. The capacitor device obtained was evaluatedin the same manner as in Example 13 and the results are shown in Tables3 and 4.

The sulfate ion content was 1.7 mol % and the4-morpholinepropanesulfonate ion content was 32 mol %, per all repeatingstructural units of the polymer. The solid electrolyte layer had anelectric conductivity of 75 S/cm.

EXAMPLE 21

A capacitor device was prepared and evaluated in the same manner as inExample 13 except for changing the 20 wt % APS used in Example 13 to 12wt % APS. The results are shown in Tables 3 and 4. The contents ofsulfate ion and 4-morpholinepropanesulfonate ion in the polymercomposition were determined according to the method described in Example13. As a result, the sulfate ion content was 0.16 mol % and the4-morpholinepropanesulfonate ion content was 25 mol %. The solidelectrolyte layer had an electric conductivity of 34 S/cm.

EXAMPLE 22

A capacitor device was prepared and evaluated in the same manner as inExample 13 except for using a sodium 2-benzimidazolepropanesulfonatesolution prepared to have the same concentration in place of sodium4-morpholinepropanesulfonate used in Example 13. The results are shownin Tables 3 and 4. The contents of sulfate ion and2-benzimidazolepropanesulfonate ion in the polymer composition weredetermined according to the method described in Example 13. As a result,the sulfate ion content was 1.8 mol % and the2-benzimidazolepropanesulfonate ion content was 14.5 mol %. The solidelectrolyte layer had an electric conductivity of 70 S/cm.

EXAMPLE 23

A capacitor device was prepared and evaluated in the same manner as inExample 13 except for using a 4-methyl-1-piperazinemethanesulfonatesolution prepared to have the same concentration in place of sodium4-morpholinepropanesulfonate used in Example 13. The results obtainedare shown in Tables 3 and 4. The contents of sulfate ion and4-methyl-1-piperazinemethanesulfonate ion in the polymer compositionwere determined according to the method described in Example 13. As aresult, the sulfate ion content was 2.0 mol % and the4-methyl-1-piperazinemethanesulfonate ion content was 16.5 mol %. Thesolid electrolyte layer had an electric conductivity of 65 S/cm.

EXAMPLE 24

A capacitor device was prepared and evaluated in the same manner as inExample 13 except for using a sodium 2,3-benzofuran-3-sulfonate solutionprepared to have the same concentration in place of sodium4-morpholinepropanesulfonate used in Example 13. The results obtainedare shown in Tables 3 and 4. The contents of sulfate ion and2,3-benzofuran-3-sulfonate ion in the polymer composition weredetermined according to the method described in Example 13. As a result,the sulfate ion content was 1.9 mol % and the 2,3-benzofuran-3-sulfonateion content was 15.8 mol %. The solid electrolyte layer had an electricconductivity of 61 S/cm.

Comparative Example 1

A solid electrolytic capacitor was manufactured in the same manner as inExample 13 except for using thiophene in place of3,4-dioxyethylenethiophene as the monomer compound used in Example 13and using a solution prepared to have a ferric chloride concentration of10 wt % in place of APS and a sodium 4-morpholinepropanesulfonateconcentration of 0.1 wt %. The capacitor device manufactured wasevaluated in the same manner as in Example 13 and the results obtainedare shown in Tables 3 and 4.

The 4-morpholinepropanesulfonate ion content in the polymer compositionwas determined according to the method described in Example 13 and foundto be 2.5 mol %. Since sulfate ion was not contained in combination, theproportion capacitor defective was high.

Comparative Example 2

A dielectric material prepared by the same forming as in Example 13 wasdipped in a 12% IPA solution of iron(III) 4-morpholinepropanesulfonateand then dipped in 1.2 mol/l of IPA solution having dissolved therein 5g of 3,4-dioxyethylene-thiophene. The resulting substrate was leftstanding in an environment of 60° C. for 10 minutes, thereby completingthe oxidation polymerization, and then the substrate was washed withwater. This polymerization reaction and the washing each was repeated 10times. The polymer composition was reduced with hydrazine in a water/IPAsolvent and carefully extracted and the 4-morpholinepropanesulfonate ionin the polymer composition was determined by an ion chromatographymethod. As a result, the 4-morpholinepropanesulfonate ion content was 15mol % per all repeating structural units of the polymer. The solidelectrolyte layer had an electric conductivity of 35 S/cm.

A formed aluminum foil was coated with this electrically conductingpolymer composition and a capacitor device was manufactured therefrom.The capacitor device was examined on the sparking voltage and othercapacitor properties according to the method described in Example 13.The results obtained are shown in Tables 3 and 4.

Comparative Example 3

A solid electrolytic capacitor was manufactured in the same manner as inExample 13 except for using a solution prepared to have a ferric sulfateconcentration of 10 wt % in place of APS used in Example 13 and a sodium4-morpholinepropanesulfonate ion concentration of 0.1 wt %. Thecapacitor device manufactured was evaluated and the results obtained areshown in Tables 3 and 4.

The contents of sulfate ion and 4-morpholinepropanesulfonate ion in thepolymer composition were determined according to the method described inExample 13. As a result, the sulfate ion content was 19.6 mol % and the4-morpholinepropanesulfonate ion content was 31.8 mol %. However, theproportion capacitor defective was high because 8 mol % of iron ion waspresent and the sulfate ion content exceeded 10 mol %.

In the sparking voltage test of Examples 13 to 24, the voltage wasscarcely reduced and the sparking voltage at the completion of reactionwas 19 V or less in any case. However, in Comparative Example 3 usingiron sulfate, the sparking voltage was greatly reduced due to iron ionremaining at a concentration as high as 8 mol % and due to the decreasein the sparking voltage before the completion of a predeterminedreaction, unsatisfactory filling of the solid electrolyte wasdisadvantageously caused.

Reference Example 3

Manufacture of a capacitor device was attempted under the sameconditions as in Example 13 except for using thiophene in place of3,4-dioxyethylenethiophene used in Example 13. However, black bluepolythiophene polymer was not produced at all, revealing that occurrenceof the oxidation polymerization of thiophenes by APS was peculiar to 3,4-dioxy group-substituted thiophenes.

TABLE 3 Sparking Voltage (unit: V, n = 5) Number of Reaction Times 1 2 34 5 6 8 10 Example 13 19 19 19 19 19 19 19 19 Example 14 19 19 19 19 1919 19 19 Example 15 19 19 19 19 19 19 19 19 Example 16 19 19 19 18 17 1412 10 Example 17 19 19 19 19 19 19 19 19 Example 18 19 19 19 19 19 19 1919 Example 19 19 19 19 19 19 19 19 19 Example 20 19 19 19 19 19 19 19 19Example 21 19 19 19 19 19 19 19 19 Example 22 19 19 19 19 19 19 19 19Example 23 19 19 19 19 19 19 19 19 Example 24 19 19 19 19 19 19 19 19Comparative 18 14 10  3 Example 1 Comparative 19 16 12  5  2 Example 2Comparative 19 16 12  3 Example 3

TABLE 4 Initial Characteristics C DF Z LC Defective/Sample Short (μF)(%) (mΩ) (μA) (units/units) Circuit Example 13 8.0 0.6 60 0.02 0/30 0Example 14 8.2 0.7 60 0.02 0/30 0 Example 15 7.9 0.8 60 0.03 0/30 0Example 16 7.2 0.8 60 0.03 0/30 0 Example 17 7.0 0.9 60 0.05 1/30 0Example 18 7.0 0.9 60 0.05 1/30 0 Example 19 4.0 1.3 60 0.09 1/30 0Example 20 7.9 0.8 60 0.03 1/30 0 Example 21 7.0 0.7 60 0.08 1/30 0Example 22 7.9 0.6 60 0.03 0/30 0 Example 23 7.9 0.7 60 0.03 0/30 0Example 24 7.8 0.8 60 0.02 0/30 0 Comparative 5.8 3.2 90 0.44 27/30  19 Example 1 Comparative 7.1 1.2 60 0.16 11/30  9 Example 2 Comparative 6.03.2 83 0.40 14/30  10  Example 3

EXAMPLE 25

A formed aluminum foil was processed to have a prescribed area and thensubjected to forming at 13 V in an aqueous 10 wt % ammonium adipatesolution to prepare a dielectric material on the aluminum foil. Thesurface of this dielectric material was dipped in an aqueous solutionprepared to have an APS concentration of 20 wt % and an ammoniumd-camphor sulfonate concentration of 0.2 wt % (Solution 1), and then thedielectric foil was dipped in 1.2 mol/l of an IPA solution havingdissolved therein 5 g of 3,4-dioxyethylenethiophene (Solution 2). Theresulting substrate was taken out and left standing in an environment at60° C. for 10 minutes, thereby completing the oxidative polymerization,and then the substrate was washed with water. This polymerizationreaction and the washing each was repeated 10 times. The polymerizationproduct was reduced with hydrazine in a water/IPA solvent and thencarefully extracted and the contents of sulfate ion and d-camphorsulfonate ion in the polymerization product were determined by an ionchromatography method. As a result, the sulfate ion content was 1.5 mol% and the d-camphor sulfonate ion content was 17 mol %, per all therepeating structural units of the polymer. The solid electrolyte layerhad an electric conductivity of 70 S/cm.

Then, the aluminum core part was welded with a plus side lead forcollecting the current from the anode and on the other hand, connectedto the minus side lead through carbon paste and silver paste forcollecting the current from the cathode. These elements were finallysealed by an epoxy resin to manufacture a capacitor device. Thecapacitor device manufactured was aged at 125° C. for 2 hours and thensubjected to the initial evaluation. The results obtained are showntogether in Table 5. In the Table 5, C indicates a capacitance and DFindicates a tangent of the loss angle (tan δ). These were each measuredat 120 Hz. The impedance is shown by a value at a resonance frequency.LC (leakage current) was measured one minute after a rated voltage wasapplied. The measured values each is an average of 30 samples. Withrespect to LC, those having an LC of 1 μA or more were judged as adefective and the average LC value was calculated exclusive of thedefective units. The results obtained in moisture resistance performancetests are shown in Table 6. Here, with respect to LC, those having an LCof 10 μA or more were judged as a shorted product and treated in thesame manner as in the case of initial value. The moisture resistanceperformance tests were carried out by leaving the capacitor device tostand under high temperature and high humidity conditions of 85° C. and85% RH for 500 hours. The reflow tests (soldering heat resistance) wereevaluated as follows. That is, 30 capacitor devices prepared werepassing through a temperature region of 230° C. for 30 seconds, and thenleakage current was measured one minute after a rated voltage wasapplied. The device having a measured value of 0.04 CV (μA) or more werejudged as a defective. Number of defective and short circuit wasexamined, and the results are shown in Table 6.

EXAMPLE 26

A capacitor device was prepared and evaluated in the same manner as inExample 25 except for using a solution of ammonium 2-camphor sulfonateprepared to have the same concentration in place of ammonium d-camphorsulfonate used in Example 25. The results obtained are shown in Tables 5and 6. The contents of sulfate ion and 2-camphor sulfonate ion in thepolymerization product were determined according to the method describedin Example 25. As a result, the sulfate ion content was 1.9 mol % andthe 2-campohr sulfonate ion content was 14 mol %. The solid electrolytelayer had an electric conductivity of 45 S/cm.

EXAMPLE 27

A capacitor device was prepared and evaluated in the same manner as inExample 25 except for using a solution of sodium d-camphor carbonate inplace of ammonium d-camphor sulfonate used in Example 25. The resultsobtained are shown in Tables 5 and 6. The contents of sulfate ion andd-camphor carbonate ion in the polymerization product were determinedaccording to the method described in Example 25 As a result, the sulfateion content was 4.7 mol % and the d-camphor carbonate ion content was4.3 mol %. The solid electrolyte layer had an electric conductivity of10 S/cm.

EXAMPLE 28

A capacitor device was prepared and evaluated in the same manner as inExample 25 except for using potassium persulfonate and N-methylpyrrolein place of APS and 3,4-dioxyethylene-thiophene, respectively, used inExample 25. The results obtained are shown in Tables 5 and 6. Thecontents of sulfate ion and d-camphor sulfonate ion in thepolymerization product were determined according to the method describedin Example 1. As a result, the sulfate ion content was 6.8 mol % and thed-camphor sulfonate ion content was 11 mol %. The solid electrolytelayer had an electric conductivity of 20 S/cm.

EXAMPLE 29

A capacitor device was prepared and evaluated in the same manner as inExample 25 except for using the following method in place of theproduction method for conducting polymer composition used in Example 25.The results obtained are shown in Tables 5 and 6. That is, a dielectricmaterial was prepared in the same manner as in Example 25 and thesurface of this dielectric material was impregnated with an dioxanesolution prepared to have an 2,3-dichloro-5,6-dicyanobenzoquione(hereafter, abbreviated DDQ) concentration of 10 wt % and an ammoniumd-camphor sulfonate concentration of 0.1 wt % (Solution 1), and then thedielectric foil was dipped in 1.2 mol/l of an IPA solution havingdissolved therein 5 g of isothianaphthene (Solution 2). The resultingsubstrate was taken out and left standing in an environment at 80° C.for 30 minutes, thereby completing the oxidative polymerization, andthen the substrate was washed with dioxane and water. Thispolymerization reaction and the washing each was repeated 10 times. Thepolymerization product was reduced with hydrazine in a water/IPA solventand then carefully extracted and the contents of d-camphor sulfonate ionin the polymerization product were determined by an ion chromatographymethod. As a result, the d-camphor sulfonate ion content was 11.5 mol %,per all the repeating structural units of the polymer. The solidelectrolyte layer had an electric conductivity of 18 S/cm.

EXAMPLE 30

A capacitor device was prepared and evaluated in the same manner as inExample 25 except for using a solution of ferric sulfate prepared to aconcentration of 10 wt % in place of APS used in Example 25. The resultsobtained are shown in Tables 5 and 6. The contents of sulfate ion andd-camphor sulfonate ion in the polymerization product were determinedaccording to the method described in Example 25. As a result, thesulfate ion content was 23 mol % and the d-camphor sulfonate ion contentwas 14 mol %. However, the existence of 11 wt % of iron element resultedin poor capacitor characteristics.

EXAMPLE 31

A capacitor device was prepared and evaluated in the same manner as inExample 25 except for using a solution prepared to have a ferricchloride concentration of 10 wt % in place of APS and a sodium d-camphorsulfonate concentration of 0.1 wt %. The results obtained are shown inTables 5 and 6. The contents of d-camphor sulfonate ion in thepolymerization product were determined according to the method describedin Example 25 and found to be 2.3 mol %. Since sulfate ion was notcontained in combination, the capacitor properties were poor.

TABLE 5 Initial Characteristics C DF Z LC Defective/Sample Short (μF)(%) (mΩ) (μA) (units/units) Circuit Example 25 5.2 0.8 26 0.04 0/30 0Example 26 5.3 0.9 24 0.04 0/30 0 Example 27 5.0 1.0 32 0.05 1/30 0Example 28 4.8 1.1 40 0.06 2/30 0 Example 29 4.7 1.2 50 0.08 2/30 0Example 30 5.4 0.6 25 0.08 1/30 0 Example 31 4.5 1.4 52 0.05 2/30 0

TABLE 6 Reflow Test moisture resistance test Defective/ Proportion ofSample Defective (units/ Short (defective/ Short units) Circuit LCsample) Circuit Example 25 0/30 0 0.14 0/30 0 Example 26 0/30 0 0.160/30 0 Example 27 0/29 0 0.20 0/29 0 Example 28 2/28 0 0.25 1/26 0Example 29 1/28 0 0.30 1/27 1 Example 30 2/29 0 0.35 0/27 0 Example 312/28 0 0.84 2/26 2

EXAMPLE 32

With respect of aluminum foil having formed thereon a solid electrolyteconsisting of an electrically conducting polymer composition which wasprepared by the method described in Example 1 to 10, 13 to 24 and 25 to31, a scanning electron micrograph of the cross sectional surface ofeach foil was examined. It is confirmed that, in the all or most of thefoils, the electrically conducting polymer covers in the form of alamellar structure the surface inside the microfine pores of dielectricmaterial and an interstitial space exist in the lamellar electricallyconducting polymer layer. For example, a micrograph of a cross-sectionobserved in Example 1 is shown in FIG. 1. The thickness of theelectrically conducting polymer layer formed on the outside surface ofthe microfine pore structure is about 5 μm and the thickness per unitlayer which constitutes the lamellar structure is in the range of about0.1 to 0.5 μm. Furthermore, it revealed that although the electricallyconducting polymer covers the entire surface inside the microfine pores,there exist voids even in these covered portions.

Industrial Applicability

As described in the foregoing, the solid electrolytic capacitor of thepresent invention comprises a solid electrolyte containing anelectrically conducting polymer having a π electron-conjugatedstructure, wherein the solid electrolyte contains as a dopant at leastone organic anion selected from (1) an alkoxy-substituted naphthalenemonosulfonate anion, (2) a sulfonate anion of a heterocyclic compound,and (3) an anion of an aliphatic polycyclic compound or a combination ofit with another anion having a dopant ability, so that a compact andhigh-performance solid electrolytic capacitor favored with low-impedanceand/or excellent sparking voltage proof properties as well as aproduction method thereof can be provided.

Furthermore, the solid electrolytic capacitor of the present inventioncomprises a solid electrolyte using a specific polyheterocycliccompound, particularly an electrically conducting polythiophenesubstituted by a dioxymethylene group, whereby there are providedeffects such that the voltage proof property (a sparking voltage test),high frequency property, tan δ, impedance property, leakage current,heat resistance (reflow property) and the like are greatly improved. Inparticular, the above-described electrically conducting polymer has acontent of the above-described organic anion of from about 0.1 to about50 mol % and a sulfate ion content of from about 0.1 to about 10 mol %,therefore, a solid electrolytic capacitor having high-performancecapacitor properties can be provided.

What is claimed is:
 1. A solid electrolytic capacitor comprising anoxide dielectric film having provided thereon an electrically conductingpolymer layer containing a π electron-conjugated structure, wherein thepolymer layer contains as a dopant at least one organic anion selectedfrom (1) an alkoxy-substituted naphthalene monosulfonate anionsubstituted by at least one linear or branched, saturated or unsaturatedalkoxy group having from 1 to 12 carbon atoms, (2) a sulfonate anion ofa heterocyclic compound having a 5- or 6-membered heterocyclic ring(hereinafter referred to as a “heterocyclic sulfonate anion”), and (3)an anion of an aliphatic polycyclic compound.
 2. The solid electrolyticcapacitor as claimed in claim 1, wherein the organic anion as a dopantis an alkoxy-substituted naphthalene monosulfonate anion substituted byat least one linear or branched, saturated or unsaturated alkoxy grouphaving from 1 to 12 carbon atoms.
 3. The solid electrolytic capacitor asclaimed in claim 2, wherein at least one hydrogen on an aromatic ring ofthe alkoxy-substituted naphthalene monosulfonate is substituted by asubstituent selected from a halogen atom, a nitro group, a cyano group,and a trihalomethyl group.
 4. The solid electrolytic capacitor asclaimed in claim 1, wherein the organic anion as a dopant is an anion ofheterocyclic sulfonate anion.
 5. The solid electrolytic capacitor asclaimed in claim 4, wherein the heterocyclic sulfonate anion is an anionhaving heterocyclic skeleton selected from the group consisting ofcompounds containing a chemical structure of morpholine, piperidine,piperazine, imidazole, furan, 1,4-dioxane, benzimidazole,benzothiazolylthio, benzisoxazole, benzotriazole or benzofuran.
 6. Thesolid electrolytic capacitor as claimed in claim 4, wherein theheterocyclic sulfonate anion contains at least one alkylsulfonatesubstituent in the chemical structure thereof.
 7. The solid electrolyticcapacitor as claimed in claim 1, wherein the organic anion as a dopantis an anion of an aliphatic polycyclic compound.
 8. The solidelectrolytic capacitor as claimed in claim 1, wherein the organic anionis contained in an amount of from about
 0. 1 to about 50 mol % based onall the repeating structural units of the electrically conductingpolymer.
 9. The solid electrolytic capacitor as claimed in claim 1,wherein in addition to the organic anion, a reductant anion of anoxidizing agent having a dopant ability is contained in an amount offrom about 0.1 to about 10 mol %.
 10. The solid electrolytic capacitoras claimed in claim 9, wherein the reductant anion of an oxidizing agentis a sulfate ion.
 11. The solid electrolytic capacitor comprising anoxide dielectric film having provided thereon an electrically conductingpolymer as claimed in claim 1, wherein the electrically conductingpolymer contains a repeating structural unit represented by thefollowing general formula (I):

(wherein the substituents R¹ and R² each independently represents anyone monovalent group selected from hydrogen, a linear or branched,saturated or unsaturated alkyl group having from 1 to 6 carbon atoms, alinear or branched, saturated or unsaturated alkoxy group having from 1to 6 carbon atoms, a hydroxyl group, a halogen atom, a nitro group, acyano group, a trihalomethyl group, a phenyl group and a substitutedphenyl group, R¹ and R² may be combined to each other at any position toform at least one divalent chain for forming at least one 5-, 6- or7-membered saturated or unsaturated ring structure, X represents ahetero atom selected from S, O, Se, Te or NR³, R³ represents hydrogen, alinear or branched, saturated or unsaturated alkyl group having from 1to 6 carbon atoms, a phenyl group or a linear or branched, saturated orunsaturated alkoxy group having from 1 to 6 carbon atoms, the alkylgroup and the alkoxy group represented by R¹, R² or R³ may optionallycontain in the chain thereof a carbonyl bond, an ether bond, an esterbond, an amide bond or an imino bond, and δ is from 0 to 1).
 12. Thesolid electrolytic capacitor as claimed in claim 11, wherein therepeating structural unit represented by formula (I) is a chemicalstructure represented by the following general formula (II):

(wherein the substituents R⁴ and R⁵ each independently representshydrogen, a linear or branched, saturated or unsaturated alkyl grouphaving from 1 to 6 carbon atoms or a substituent for forming at leastone 5-, 6- or 7-membered heterocyclic structure containing the twooxygen elements shown in the formula by combining the linear orbranched, saturated or unsaturated alkyl groups having from 1 to 6carbon atoms to each other at any position, the ring structure formed inthe scope thereof includes a chemical structure such as a substitutedvinylene group and a substituted o-phenylene group, and δ is from 0 to1).
 13. The solid electrolytic capacitor as claimed in claim 1, whereinthe solid electrolyte has at a portion which is of a lamellar structure.14. The solid electrolytic capacitor as claimed in claim 13, wherein thesolid electrolyte having at a portion which is of a lamellar structureis formed on an outer surface of the dielectric film or on an outersurface and inside a fine pore portion thereof.
 15. The solidelectrolytic capacitor as claimed in claim 13, wherein adjacent lamellaedefine an interstitial space therebetween over at least a portion ofopposing surfaces thereof.
 16. The solid electrolytic capacitor asclaimed in claim 13, wherein each lamella of the solid electrolyteconstituting the lamellar structure is in the range of from about 0.01to about 5 μm, and the solid electrolyte layer has a total thickness inthe range of from about 1 to about 200 μm.